This application relates most specifically to improved overpouches typically for parenteral solution containers or other medical items as may be desired.
Currently, some parenteral solution containers are made of polyvinyl chloride, being enclosed in a modified polyethylene overpouch to reduce water loss from the solution container by permeation during long-term storage, since the overpouch provides a good vapor barrier.
The above overpouch is transparent, but noticeably milky and not crystal clear. Although the solution container can be easily viewed through the overpouch, it is deemed desirable by some sources, particularly in some foreign countries, to have an overpouch for parenteral solution containers which is crystal clear, and yet which provides the desired autoclavability, good water vapor barrier properties and good overall physical integrity.
Furthermore, it would be desirable to increase the inside volume of the overpouch by preforming a bulge in one of the sheet faces of the overpouch by a thermoforming process or the like. This is not easily accomplished with polypropylene sheeting, particularly biaxially oriented polypropylene sheeting which has the desirable clarity and strength.
In Gajewski et al. U.S. Pat. No. 4,210,686, a multilayered plastic sheeting is disclosed having high clarity, strength, and resistance to water vapor transmission. However, the sheet material at the desirable thin grade used for the production of flexible overpouches can exhibit difficulties during heat sealing operations on an automated basis. The heat seal dies can easily melt through the heat seals when the multiple layers of the plastic sheeting all have similar melting points. Accordingly, while the material of the above cited patent can be readily heat sealed to form containers, it is a fairly critical operation which is difficult to maintain in automated equipment such as a horizontal form-fill machine, where laminated materials of substantially different melting points are preferred for heat sealing.
In accordance with this invention, a new laminated container structure is provided, which preferably is utilized as an overpouch for a medical container or the like, in which the opposed sides of the overpouch, peripherally sealed about their edges, constitute differing, preferably laminated materials, each of which provide unique advantages to the entire system to obtain a superior container product of essentially optically clear transparency, good flexibility, good heat sealing and water vapor barrier properties, and high flex crack resistance. The container of this invention may also be a primary container for liquids or the like if desired.